Field
The teachings in accordance with the exemplary embodiments of this disclosure relate generally to an apparatus of adjusting valve timing for internal combustion engine and a method thereof, and more particularly to an apparatus of adjusting valve timing for internal combustion engine configured to improve engine performance by increasing reliability of locking operation and a method thereof.
Background
In general, an apparatus of valve timing adjusting (hereinafter referred to as “apparatus of adjusting valve timing, or simply as “apparatus”) has been used that is capable of changing a timing of an intake valve or an exhaust valve in response to operation state of an internal combustion engine (hereinafter referred to as “engine”). The valve timing adjusting apparatus changes a timing of intake valve or exhaust valve by changing a displacement angle or a rotation phase of a cam shaft interacting with a crank shaft via a timing belt or a chain, and various types of apparatuses are proposed.
In general, vane type valve timing adjusting apparatuses including a rotor having a plurality of vanes, e.g., three or four vanes freely rotated inside a housing by working fluid, are largely used. Among these apparatuses, a valve timing adjusting apparatus, i.e., an intermediate phase valve timing adjusting apparatus, is largely used in terms of efficiency aspect, where an engine is started by interaction with a crank shaft while a cam shaft is locked using a locking pin when the cam shaft is positioned at an intermediate position between a full advance phase angle and a full retard phase angle relative to the crank shaft.
Meantime, the locking method of using the locking pin may be categorized into a method using a hydraulic ratchet operated by oil, and a method using a mechanical ratchet. The hydraulic ratchet method is complicated in flow path albeit being small in oil consumption, while the mechanical ratchet method is widely used because of being simple in structure albeit being of more consumption in oil than the hydraulic ratchet method.
For example, the Japanese laid open patent No. 2001-50016 discloses a valve timing adjusting apparatus configured to prevent generation of noise and to quickly start an engine at an intermediate position, and the Japanese laid open patent No. 2000-2104 discloses a valve timing adjusting apparatus configured to prevent generation of noise. Furthermore, the Japanese laid open patent No. 2002-357105 discloses a valve timing adjusting apparatus having two locking pins in which the locking pin is divided to one pin controlling a retard phase angle operation and another pin controlling an advance phase angle.
The valve timing adjusting apparatus mentioned above is of an external-mounting type structure in which a hydraulic control valve to adjust a flow direction of working fluid supplied to a rotor is mounted on a cylinder head in order to increase or delay the timing of intake valve or exhaust valve.
Meantime, the external-mounting type valve timing adjusting apparatus suffers from disadvantages in that flow resistance to flow of working fluid may be generated or leakage may be generated due to lengthened distance between the hydraulic control valve and the valve timing adjusting apparatus mounted with a rotor inside a housing, whereby responsiveness of the valve timing adjusting apparatus is reduced by pressure decrease in the working fluid. Another disadvantage is that a hydraulic pressure circuit for arranging a hydraulic control valve on a cylinder head becomes complicated.
On top of that, when an intermediate phase valve timing adjusting apparatus is applied to the external-mounting type structure, an additional control valve or a hydraulic pressure circuit may be required in certain cases in order to control the operation of locking pin, which adds the complexity of design to configuration and operation.
In order to solve the aforementioned disadvantages, an internal-mounting (center feed) type valve timing adjusting apparatus, in which a hydraulic control valve is integrally mounted inside a fixing bolt of a rotor, has been developed, which is compact in the entire configuration of valve timing adjusting apparatus and simple in external piping as well.
For example, the Japanese Laid-open patent No. 2010-285986 discloses a valve timing adjusting apparatus capable of quickly adjusting valve timing by improving an operational structure of hydraulic control valve. However, the valve timing adjusting apparatus of the Japanese Laid-open patent No. 2010-285986 also suffers drawbacks in that although a bad influence, in which surging of working fluid affects the locking operation, can be removed to allow a quick control of valve timing, configuration of rotor becomes complicated due to structure of employing two locking pins, and improved reliability of operation is limited due to increased number of component parts.
Thus, various valve timing adjusting apparatuses for internal combustion engine have been developed that can improve an engine performance by efficiently adjusting a valve timing while locking and releasing operations with good responsiveness and high reliability can be realized using a simple configuration.
The present applicant has proposed a valve timing adjusting apparatus of an internal combustion engine through Korean patent application Nos.: 10-2015-0185229 and 10-2016-0001689, and therefore, it is preferable that development of a hydraulic control technique be required in order to improve responsiveness of operation and increase reliability for a valve timing adjusting apparatus.